Lithography machine alignment control method based on an asynchronous state machine

Abstract

Provided is a lithography machine alignment control method based on an asynchronous state machine. The lithography machine alignment control method based on the asynchronous state machine comprises: starting an asynchronous state machine in response to a lithography machine alignment process starting; performing loading of a mask plate on a mask plate stage and loading of a wafer on a wafer stage in parallel based on the asynchronous state machine; and the asynchronous state machine synchronizing completion of the loading of the mask plate on the mask plate stage and the loading of the wafer on the wafer stage, and triggering sequential execution of mask plate fine alignment, wafer leveling and focusing, and wafer alignment. In this way, the asynchronous state machine solves the problem of different state changes not being synchronized in the lithography machine alignment control process, while achieving concurrent and synchronous control of some states, thereby improving alignment efficiency, flexibility of use, and expandability.

Description

Technical Field

[0001] This application relates to the field of lithography machine technology, and more specifically, to a lithography machine alignment control method based on an asynchronous state machine. Background Technology

[0002] Alignment control in lithography is a crucial technology used during the lithography process to ensure the alignment accuracy between the photomask and the silicon wafer. It guarantees perfect alignment between the patterns on the photomask and the patterns on the silicon wafer, enabling precise pattern transfer. The accuracy and stability of alignment control are critical to semiconductor chip manufacturing, as they directly impact chip quality and performance. Therefore, lithography machine manufacturers and semiconductor manufacturing companies are continuously researching and improving alignment control technologies to enhance alignment accuracy and efficiency.

[0003] Alignment control in lithography machines is a complex process, and improving alignment efficiency involves addressing concurrency and synchronization issues. The challenge lies in flexibly controlling each step of the alignment process and efficiently completing the alignment, while also acknowledging that the alignment methods may vary slightly depending on the type of lithography machine.

[0004] Therefore, the problem that needs to be solved is how to simplify the complex alignment process and achieve alignment efficiently and quickly, while adapting to the expansion and reuse of different alignment methods.

[0005] Therefore, it is desirable to provide an improved alignment control scheme for lithography machines. Summary of the Invention

[0006] This application provides a lithography machine alignment control method based on an asynchronous state machine. It solves the problem of asynchronous state changes in the alignment control process of the lithography machine by using an asynchronous state machine, and realizes concurrent synchronous control of some states, thereby improving alignment efficiency, flexibility and scalability.

[0007] According to one aspect of this application, a lithography machine alignment control method based on an asynchronous state machine is provided, comprising: starting an asynchronous state machine in response to the start of the lithography machine alignment process; performing photomask loading on a photomask stage and silicon wafer loading on a silicon wafer stage in parallel based on the asynchronous state machine; and the asynchronous state machine synchronizing the completion of photomask loading on the photomask stage and silicon wafer loading on the silicon wafer stage, and triggering sequential execution of photomask fine alignment, silicon wafer leveling and focusing, and silicon wafer alignment.

[0008] In the above-mentioned lithography machine alignment control method based on asynchronous state machine, the photomask loading of the photomask stage includes photomask preloading, photomask stage loading, and photomask coarse alignment.

[0009] In the above-mentioned lithography machine alignment control method based on asynchronous state machines, the photomask preloading includes the asynchronous state machine entering the photomask loading state (as a preceding state) from the alignment start state (as a following state) and performing a loading operation; the photomask stage loading includes the asynchronous state machine entering the stage photomask loading state (as a preceding state) from the photomask loading state (as a following state) and performing a loading operation; and the photomask coarse alignment includes the asynchronous state machine entering the stage photomask loading state (as a preceding state) from the stage photomask loading state (as a following state) and performing a coarse alignment operation.

[0010] In the above-mentioned lithography machine alignment control method based on asynchronous state machine, the silicon wafer loading of the silicon wafer stage includes: parallel execution of reference mark focusing and silicon wafer preloading based on the asynchronous state machine; synchronous triggering of silicon wafer stage loading upon completion of reference mark focusing and silicon wafer preloading based on the asynchronous state machine; and sequential execution of silicon wafer stage alignment after silicon wafer stage loading.

[0011] In the above-described lithography machine alignment control method based on an asynchronous state machine, the reference mark focusing includes the asynchronous state machine transitioning from an alignment start state (as a preceding state) to a reference mark focusing state (as a following state) and performing a focusing operation; the silicon wafer preloading includes the asynchronous state machine transitioning from an alignment start state (as a preceding state) to a silicon wafer loading state (as a following state) and performing a loading operation; the silicon wafer loading onto the worktable includes the asynchronous state machine synchronously transitioning from the reference mark focusing state (as a preceding state) and the silicon wafer loading state to a worktable silicon wafer loading state (as a following state) and performing a loading operation; and the silicon wafer worktable alignment includes the asynchronous state machine transitioning from the aforementioned worktable silicon wafer loading state (as a preceding state) to a worktable alignment state (as a following state) and performing a worktable alignment operation.

[0012] In the above-mentioned lithography machine alignment control method based on asynchronous state machines, the photomask fine alignment includes the asynchronous state machine synchronously entering the photomask fine alignment state (as a preceding state) and the stage alignment state (as a following state) and performing the photomask fine alignment operation; the silicon wafer leveling and focusing includes the asynchronous state machine entering the silicon wafer leveling and focusing state (as a following state) from the photomask fine alignment state (as a preceding state) and performing the silicon wafer leveling and focusing operation; and the silicon wafer alignment includes the asynchronous state machine entering the silicon wafer alignment state (as a following state) from the silicon wafer leveling and focusing state (as a preceding state) and performing the silicon wafer alignment operation.

[0013] In the above-mentioned lithography machine alignment control method based on asynchronous state machine, the asynchronous state machine includes: a state manager for logic implementation and maintenance of automatic state transitions and state transition monitoring; a state converter for defining business state transitions; a state listener for listening to state changes; and a state machine controller for registering the state manager of the asynchronous state machine and finding the corresponding state manager for concurrent state processing.

[0014] This application provides a lithography machine alignment control method based on an asynchronous state machine. It solves the problem of asynchronous state changes in the alignment control process of the lithography machine by using an asynchronous state machine, and realizes concurrent synchronous control of some states, thereby improving alignment efficiency, flexibility and scalability. Attached Figure Description

[0015] Various other advantages and benefits of this application will become apparent to those skilled in the art upon reading the detailed description of the preferred embodiments below. The accompanying drawings are for illustrative purposes only and are not intended to limit the scope of this application. It is obvious that the drawings described below are merely some embodiments of this application, and those skilled in the art can obtain other drawings based on these drawings without any inventive effort. Furthermore, the same reference numerals denote the same parts throughout the drawings.

[0016] Figure 1 The figure shows a schematic flowchart of a lithography machine alignment control method based on an asynchronous state machine according to an embodiment of this application.

[0017] Figure 2 The figure shows a schematic diagram of each module of the lithography machine alignment control system based on an asynchronous state machine according to an embodiment of this application.

[0018] Figure 3 The figure shows a schematic diagram of the component implementation of the asynchronous state machine in the lithography machine alignment control method based on the asynchronous state machine according to an embodiment of this application.

[0019] Figure 4 The figure illustrates the state transitions and behavioral operations of the asynchronous state machine in the lithography machine alignment control method based on the asynchronous state machine according to an embodiment of this application. Detailed Implementation

[0020] Hereinafter, exemplary embodiments according to this application will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments of this application. It should be understood that this application is not limited to the exemplary embodiments described herein.

[0021] Figure 1The figure shows a schematic flowchart of a lithography machine alignment control method based on an asynchronous state machine according to an embodiment of this application.

[0022] like Figure 1 As shown, the lithography machine alignment control method based on an asynchronous state machine according to an embodiment of this application includes the following steps.

[0023] Step S110: In response to the start of the lithography machine alignment process, the asynchronous state machine is initiated. Here, Figure 2 The diagram illustrates the modules of a lithography machine alignment control system based on an asynchronous state machine according to an embodiment of this application. Figure 2 As shown, when the lithography machine alignment control system receives a lithography machine alignment request based on the user interface (UI), the lithography machine main control center, which is mainly used to process requests sent by the user interface or other terminal interfaces, starts the lithography machine alignment process. At this time, the lithography machine main control center controls the start of the asynchronous state machine.

[0024] In this embodiment, the asynchronous state machine can functionally divide state managers according to the business process, execute different operations under different business states, and flexibly switch between state managers of different businesses. Specifically, for each state change, a synchronous state machine must wait for other states to complete their changes and enter the next state. The asynchronous state machine, however, allows asynchronous changes between states; that is, a change in one state will not affect changes in other states.

[0025] For the specific lithography alignment process, since it involves the coordinated work of the photomask stage, the silicon wafer stage, and the alignment sensor to finally complete the alignment, the silicon wafer stage is a resource that is in competition. However, the photomask stage (RS: Reticle Stage) and the silicon wafer stage (WS: Wafer Stage) are two independent devices that can work concurrently. That is to say, each of them maintains its own state changes, but at the same time, they need to be synchronously controlled to trigger the next state.

[0026] Specifically, after the asynchronous state machine is started, it can enter a predetermined state, such as aligning to the start state, and perform the start operation.

[0027] Step S120: Based on the asynchronous state machine, the photomask loading of the photomask stage and the silicon wafer loading of the silicon wafer stage are executed in parallel. That is, as described above, since the photomask stage and the silicon wafer stage are two independent devices that can operate concurrently, in the lithography machine alignment control method based on the asynchronous state machine according to the embodiments of this application, by executing photomask preloading and silicon wafer preloading based on the asynchronous state machine, both can independently perform the alignment process based on their own state changes.

[0028] Specifically, the photomask loading process on the photomask loading stage includes photomask preloading, photomask loading onto the photomask loading stage, and photomask coarse alignment. Photomask preloading refers to the process of the photomask moving from the photomask storage area to the photomask pre-alignment stage; photomask loading onto the photomask loading stage refers to the process of the photomask moving from the photomask pre-alignment stage to the mounting point on the photomask loading stage; and photomask coarse alignment refers to the coarse alignment of the photomask on the photomask loading stage using alignment sensors. In other words, the photomask loading process on the photomask loading stage sequentially executes photomask preloading, photomask loading onto the photomask loading stage, and photomask coarse alignment.

[0029] Here, during photomask preloading, the asynchronous state machine transitions from the alignment start state (preceding state) to the photomask loading state (following state) and performs the loading operation. During photomask loading on the worktable, the asynchronous state machine transitions from the photomask loading state (preceding state) to the worktable photomask loading state (following state) and performs the loading operation. During coarse photomask alignment, the asynchronous state machine transitions from the worktable photomask loading state (preceding state) to the coarse alignment state (following state) and performs the coarse alignment operation.

[0030] Therefore, in the lithography machine alignment control method based on asynchronous state machine according to the embodiments of this application, the photomask loading on the photomask stage includes photomask preloading, photomask stage loading, and photomask coarse alignment.

[0031] Furthermore, in the aforementioned lithography machine alignment control method based on asynchronous state machines, the photomask preloading includes the asynchronous state machine transitioning from the alignment start state (a preceding state) to the photomask loading state (a following state) and performing a loading operation; the photomask stage loading includes the asynchronous state machine transitioning from the photomask loading state (a preceding state) to the stage photomask loading state (a following state) and performing a loading operation; and the photomask coarse alignment includes the asynchronous state machine transitioning from the stage photomask loading state (a preceding state) to the photomask coarse alignment state (a following state) and performing a coarse alignment operation.

[0032] On the other hand, the silicon wafer loading process of the silicon wafer stage includes Fiducial Mark (FM) focusing, silicon wafer preloading, wafer placement on the silicon wafer stage, and silicon wafer stage alignment. Fiducial Mark focusing refers to the process of focusing the Fiducial Mark on the silicon wafer stage using a focusing sensor to improve the photomask alignment accuracy. Silicon wafer preloading refers to the process of moving the silicon wafer from the wafer storage area to its waiting position on the silicon wafer stage. Therefore, it can be seen that in the silicon wafer loading process of the silicon wafer stage, Fiducial Mark focusing and silicon wafer preloading can also be executed in parallel based on the aforementioned asynchronous state machine.

[0033] In addition, as mentioned above, the asynchronous state machine allows for different state changes during the reference mark focusing and silicon wafer preloading process. After the reference mark focusing and silicon wafer preloading are completed, synchronous control is then performed to trigger the silicon wafer stage to be mounted and aligned with the silicon wafer stage.

[0034] Among them, wafer loading on the silicon wafer worktable refers to the business process of moving the silicon wafer from the waiting position on the silicon wafer worktable to the receiving position on the silicon wafer worktable, and wafer alignment on the silicon wafer worktable refers to the business process of aligning the reference marks on the silicon wafer worktable with the alignment sensor.

[0035] Here, during reference mark focusing, the asynchronous state machine transitions from the alignment start state (preceding state) to the reference mark focusing state (following state) and performs the focusing operation. During wafer preloading, the asynchronous state machine transitions from the alignment start state (preceding state) to the wafer loading state (following state) and performs the loading operation. During wafer stage loading, the asynchronous state machine synchronizes the reference mark focusing state (preceding state) and the wafer loading state to the stage wafer loading state (following state) and performs the loading operation. During wafer stage alignment, the asynchronous state machine transitions from the stage wafer loading state (preceding state) to the stage alignment state (following state) and performs the stage alignment operation.

[0036] Therefore, in the lithography machine alignment control method based on an asynchronous state machine according to the embodiments of this application, the silicon wafer loading of the silicon wafer stage includes: performing reference mark focusing and silicon wafer preloading in parallel based on the asynchronous state machine; triggering the silicon wafer stage to be mounted on the asynchronous state machine upon completion of the synchronous reference mark focusing and silicon wafer preloading; and sequentially performing silicon wafer stage alignment after the silicon wafer stage is mounted on the asynchronous state machine.

[0037] Furthermore, in the aforementioned lithography machine alignment control method based on asynchronous state machines, the reference mark focusing includes the asynchronous state machine transitioning from an alignment start state (as a preceding state) to a reference mark focusing state (as a following state) and performing a focusing operation; the silicon wafer preloading includes the asynchronous state machine transitioning from an alignment start state (as a preceding state) to a silicon wafer loading state (as a following state) and performing a loading operation; the silicon wafer stage loading includes the asynchronous state machine synchronously transitioning from the reference mark focusing state (as a preceding state) and the silicon wafer loading state to a stage silicon wafer loading state (as a following state) and performing a loading operation; and the silicon wafer stage alignment includes the asynchronous state machine transitioning from the stage silicon wafer loading state (as a preceding state) to a stage alignment state (as a following state) and performing a stage alignment operation.

[0038] In step S130, the asynchronous state machine synchronizes the completion of photomask loading on the photomask worktable and silicon wafer loading on the silicon wafer worktable, and triggers the sequential execution of photomask fine alignment, silicon wafer leveling and focusing, and silicon wafer alignment.

[0039] Here, the precise alignment of the photomask refers to the precise alignment of the photomask on the photomask stage using an alignment sensor. Therefore, since this simultaneously occupies resources on both the photomask stage and the wafer stage, an asynchronous state machine is needed to synchronously control the loading of the photomask on the photomask stage and the wafer on the wafer stage to perform the precise alignment. In contrast, as mentioned above, since coarse alignment of the photomask does not occupy the wafer stage, it can be processed in parallel based on separate states of the asynchronous state machine.

[0040] In addition, the silicon wafer leveling and focusing refers to the business process of leveling and focusing the silicon wafer before alignment using a leveling and focusing sensor in order to improve the alignment accuracy of the silicon wafer, and the silicon wafer alignment refers to the business process of aligning the silicon wafer on the silicon wafer worktable using an alignment sensor.

[0041] During photomask fine alignment, the asynchronous state machine synchronizes the photomask coarse alignment state (preceding state) and the stage alignment state to the photomask fine alignment state (following state), and performs the photomask fine alignment operation. During silicon wafer leveling and focusing, the asynchronous state machine transitions from the aforementioned photomask fine alignment state (preceding state) to the silicon wafer leveling and focusing state (following state), and performs the silicon wafer leveling and focusing operation. During silicon wafer alignment, the asynchronous state machine transitions from the aforementioned silicon wafer leveling and focusing state (preceding state) to the silicon wafer alignment state (following state), and performs the silicon wafer alignment operation, thus ending the lithography machine alignment control process.

[0042] Therefore, in the lithography machine alignment control method based on an asynchronous state machine according to the embodiments of this application, the photomask fine alignment includes the asynchronous state machine synchronously entering the photomask fine alignment state as a preceding state and the stage alignment state as a following state and performing the photomask fine alignment operation; the silicon wafer leveling and focusing includes the asynchronous state machine entering the silicon wafer leveling and focusing state as a following state from the photomask fine alignment state as a preceding state and performing the silicon wafer leveling and focusing operation; and the silicon wafer alignment includes the asynchronous state machine entering the silicon wafer alignment state as a following state from the silicon wafer leveling and focusing state as a preceding state and performing the silicon wafer alignment operation.

[0043] Based on this, the asynchronous state machine performs state transitions and executes operations between preceding and subsequent states through start states, termination states, and non-termination states. Specifically, considering resource mutual exclusion, except for silicon wafer preloading and photomask preloading, which are controlled by other devices, other alignment states are configured with two main lines that can be synchronously controlled, as well as state change monitoring. That is, the states based on the photomask stage can be divided into: photomask coarse alignment, photomask fine alignment, and photomask mounting, while the states based on the silicon wafer stage can be divided into: silicon wafer mounting, silicon wafer alignment, reference mark focusing, stage focusing, and silicon wafer leveling and focusing. Therefore, the specific component configuration of the asynchronous state machine according to the embodiments of this application is as follows: Figure 3 As shown. Here, Figure 3 The figure shows a schematic diagram of the component implementation of the asynchronous state machine in the lithography machine alignment control method based on the asynchronous state machine according to an embodiment of this application.

[0044] like Figure 3 As shown, the components of the asynchronous state machine include: StateManager, used for implementing the main logic, maintaining automatic state transitions (non-final state -> final state), and monitoring state transitions; StateTransition, which defines the state transitions for each business function, including previous states, actions, and subsequent states, where actions are processed asynchronously; StateListen, used to listen for state changes, i.e., to listen for events that trigger state changes; and StateMachine, responsible for registering all state managers in the asynchronous state machine and finding the corresponding state managers for concurrent state processing. These four components work together to ensure that the state synchronization of the entire asynchronous state machine remains consistent, controlling the flexible flow between various business functions, and ensuring that inserting or deleting any business state does not affect other business states.

[0045] Therefore, in the lithography machine alignment control method based on an asynchronous state machine according to the embodiments of this application, the asynchronous state machine includes: a state manager for logic implementation and maintenance of automatic state transitions and state transition monitoring; a state converter for defining business state transitions; a state listener for listening to state changes; and a state machine controller for registering the state manager of the asynchronous state machine and finding the corresponding state manager for concurrent state processing.

[0046] Figure 4 The illustration shows the state transitions and behavioral operations of the asynchronous state machine in the lithography machine alignment control method based on an asynchronous state machine according to an embodiment of this application. Here, Figure 4 The content has already been explained in detail above, so it will not be repeated here to avoid redundancy.

[0047] In summary, the lithography machine alignment control method based on asynchronous state machines according to the embodiments of this application solves the problem of asynchronous state changes on different control main lines by using asynchronous state machines, enabling simultaneous concurrent synchronous control of some states. For the lithography machine alignment control process, alignment efficiency can be improved through synchronous control of photomask coarse alignment and workpiece stage alignment, maximizing resource utilization. Synchronously controlling the business process with two main lines effectively improves concurrency. Furthermore, from a flexibility perspective, since changes in the state manager do not cause changes to the state machine control code, code reuse is possible. The business process can be modified through configuration without requiring code changes, achieving code flexibility based on high configurability. In addition, from a business scalability perspective, for example, adding a baseline detection business process only requires adding the implementation of the pre-state, post-state, and actions; the state transitions do not affect other parts.

[0048] The basic principles of this application have been described above with reference to specific embodiments. However, it should be noted that the advantages, benefits, and effects mentioned in this application are merely examples and not limitations, and should not be considered as essential features of each embodiment of this application. Furthermore, the specific details disclosed above are for illustrative and facilitative purposes only, and are not limitations. These details do not limit the application to the necessity of employing the aforementioned specific details for implementation.

[0049] The block diagrams of devices, apparatuses, devices, and systems involved in this application are merely illustrative examples and are not intended to require or imply that they must be connected, arranged, or configured in the manner shown in the block diagrams. As those skilled in the art will recognize, these devices, apparatuses, devices, and systems can be connected, arranged, and configured in any manner. Words such as “comprising,” “including,” “having,” etc., are open-ended terms meaning “including but not limited to,” and are used interchangeably with them. The terms “or” and “and” as used herein refer to the terms “and / or,” and are used interchangeably with them unless the context clearly indicates otherwise. The term “such as” as used herein refers to the phrase “such as but not limited to,” and is used interchangeably with it.

[0050] It should also be noted that in the apparatus, equipment, and methods of this application, the components or steps can be disassembled and / or recombined. These disassemblies and / or recombinations should be considered as equivalent solutions of this application.

[0051] The above description of the disclosed aspects is provided to enable any person skilled in the art to make or use this application. Various modifications to these aspects will be readily apparent to those skilled in the art, and the general principles defined herein can be applied to other aspects without departing from the scope of this application. Therefore, this application is not intended to be limited to the aspects shown herein, but rather to be accorded the widest scope consistent with the principles and novel features disclosed herein.

[0052] The above description has been given for purposes of illustration and description. Furthermore, this description is not intended to limit the embodiments of this application to the forms disclosed herein. Although numerous exemplary aspects and embodiments have been discussed above, those skilled in the art will recognize certain variations, modifications, alterations, additions, and sub-combinations thereof.

Claims

1. A lithography machine alignment control method based on an asynchronous state machine, comprising: In response to the start of the lithography machine alignment process, the asynchronous state machine is initiated. The asynchronous state machine performs state transitions between the previous state and the next state and executes operations; Based on the asynchronous state machine, the photomask loading of the photomask stage and the silicon wafer loading of the silicon wafer stage are performed in parallel; and The asynchronous state machine synchronizes the completion of photomask loading on the photomask worktable and silicon wafer loading on the silicon wafer worktable, and triggers the sequential execution of photomask fine alignment, silicon wafer leveling and focusing, and silicon wafer alignment. The silicon wafer loading of the silicon wafer stage includes: Based on the asynchronous state machine, the reference mark focusing and silicon wafer preloading are performed in parallel. Based on the asynchronous state machine, the focus is triggered upon completion of the synchronous reference mark focusing and silicon wafer preloading; and, after the silicon wafer is mounted on the silicon wafer stage, silicon wafer stage alignment is performed sequentially.

2. The lithography machine alignment control method based on asynchronous state machine as described in claim 1, wherein, The photomask loading process on the photomask worktable includes photomask preloading, photomask loading onto the photomask worktable, and photomask coarse alignment.

3. The lithography machine alignment control method based on asynchronous state machine as described in claim 2, wherein, The photomask preloading includes the asynchronous state machine entering the photomask loading state, which is the preceding state, from the alignment start state, which is the following state, and performing the loading operation. The photomask loading process on the workbench includes the asynchronous state machine transitioning from a previous state (photomask loading state) to a subsequent state (workbench photomask loading state) and performing the loading operation; and... The photomask coarse alignment includes the asynchronous state machine transitioning from the worktable photomask loading state (preceding state) to the photomask coarse alignment state (following state) and performing the coarse alignment operation.

4. The lithography machine alignment control method based on asynchronous state machine as described in claim 1, wherein, The reference mark focusing includes the asynchronous state machine entering the reference mark focusing state as the follow-up state from the alignment start state as the previous state and performing the focusing operation. The silicon wafer preloading includes the asynchronous state machine entering the silicon wafer loading state as a subsequent state from the alignment start state as a preceding state and performing the loading operation. The silicon wafer loading stage includes the asynchronous state machine synchronizing the reference mark focusing state and the silicon wafer loading state as the previous state to enter the silicon wafer loading state as the subsequent state and perform the loading operation; and... The silicon wafer stage alignment includes the asynchronous state machine transitioning from the silicon wafer loading state (pre-stage) to the stage alignment state (post-stage) and performing the stage alignment operation.

5. The lithography machine alignment control method based on asynchronous state machine as described in claim 1, wherein, The photomask fine alignment includes the asynchronous state machine synchronizing the photomask coarse alignment state and the worktable alignment state as the previous state to enter the photomask fine alignment state as the subsequent state and perform the photomask fine alignment operation. The silicon wafer leveling and focusing includes the asynchronous state machine transitioning from the photomask fine alignment state (as a pre-position) to the silicon wafer leveling and focusing state (as a post-position) and performing the silicon wafer leveling and focusing operation. as well as, The silicon wafer alignment includes the asynchronous state machine transitioning from the silicon wafer leveling and focusing state (as a preceding state) to the silicon wafer alignment state (as a following state) and performing the silicon wafer alignment operation.

6. The lithography machine alignment control method based on an asynchronous state machine as described in claim 1, wherein, The asynchronous state machine includes: A state manager is used for logic implementation and maintenance of automatic state transitions and state transition monitoring. State converters are used to define business state transitions; A state listener is used to monitor state changes; a state machine controller is used to register the state manager of the asynchronous state machine and to find the corresponding state manager for concurrent state processing.

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